This invention optimizes the location of a center of mass of an orbiting scroll, by adding or removing material at certain strategic locations on the orbiting scroll.
Scroll compressors are widely applied in refrigerant compression applications. In a scroll compressor, a pair of scroll members each have a base with a spiral wrap extending from the base. The wraps of the two scroll members interfit to define compression chambers. A shaft drives one of the scroll members to orbit relative to the other.
Scroll compressors are provided with counterweights mounted on the shaft to counteract vibration that would otherwise occur, mainly due to mass imbalance caused by orbiting motion of the orbiting scroll.
While overall compressor vibration is minimized by proper selection and location of shaft counterweights, there can be an alternating torsional moment acting on an Oldham coupling in the scroll compressor. This moment cannot be balanced by shaft counterweights. This alternating moment can cause coupling chatter that in turn increases radiated sound, which is undesirable.
The purpose of this invention is to reduce coupling chatter by shifting the center of mass of the orbiting scroll. The orbiting scroll center of mass is shifted in such a way as to compensate for the torsional moment acting on the coupling.
The unwanted torsional moment can be a result of the center of mass of the orbiting scroll not being coincidental with its geometric center or due to variations in the generating radius of a scroll wrap profile. The scroll wrap profile, typical of refrigeration applications, will often have a generating radius that is not constant. This is a result of a wrap profile being represented by an involute other than an involute of a circle.
In disclosed embodiments of this invention, a scroll compressor is designed to minimize the alternating torsional moment acting on the coupling by adding or removing mass at selected locations on the orbiting scroll such that the orbiting scroll center of mass is at a desired location. The desired location may sometimes be at the geometric center of orbiting scroll for an involute of a circle wrap profile. Alternatively, the center of mass is sometimes offset from the geometric center to compensate for peculiarities of scroll wrap profile design, such as varying generating radius.
In a first embodiment, the shift in center of mass is achieved by removing mass from the base of the orbiting scroll through introduction of circular indentations that for example can be conveniently created by drilling or milling operation. The size and location of the indentations must be carefully selected to achieve proper center of mass location.
In another embodiment, mass is removed from a non-working portion of the outer flank of a scroll wrap. In yet another embodiment, mass can be removed from the outer periphery of the base of the scroll member.
In additional embodiments, mass could be added to any of the above locations, or other locations within the scroll member.
The basic invention is a method of designing an orbiting scroll member wherein the center of mass gravity is ideally located by adding or removing mass at selected locations. The exact location and amount of mass removed or added would vary with the particular scroll compressor design and particular design goal. However, a worker of ordinary skill in the art would recognize how to optimize the required amount and location of orbiting scroll removed mass or added mass, based upon the teachings of this invention.
Further features of this invention can be best understood from the following specification and drawings, the following of which is a brief description.